Soft filled prosthesis shell with discrete fixation surfaces

ABSTRACT

A soft prosthetic implant shell, such as a silicone breast implant shell, that has discrete fixation surfaces thereon for tissue adhesion. The fixation surfaces may be provided on the posterior face of the shell, as well as either on the periphery or at discrete areas on the anterior face. Band-shaped fixation surfaces may be provided on the anterior face of the shell to generally match the angle of pectoralis major or pectoralis minor muscle groups. The fixation surfaces may be roughened areas of the shell, or may be separate elements adhered to the shell.

CROSS REFERENCE

This application is a continuation of U.S. patent application Ser. No.12/540,317, filed Aug. 12, 2009, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/088,418, filed on Aug. 13,2008, the entire disclosures of which are incorporated herein by thisspecific reference.

FIELD OF THE INVENTION

The present invention relates to soft prosthetic implants and, moreparticularly, to textured exterior surfaces of such implants, forinstance, breast implants.

BACKGROUND OF THE INVENTION

Implantable prostheses are commonly used to replace or augment bodytissue. In the case of breast cancer, it is sometimes necessary toremove some or all of the mammary gland and surrounding tissue, whichcreates a void that can be filled with an implantable prosthesis. Theimplant serves to support surrounding tissue and to maintain theappearance of the body. The restoration of the normal appearance of thebody has an extremely beneficial psychological effect on post-operativepatients, eliminating much of the shock and depression that oftenfollows extensive surgical procedures. Implantable prostheses are alsoused more generally for restoring the normal appearance of soft tissuein various areas of the body, such as the buttocks, chin, calf, etc.

Soft implantable prostheses typically include a relatively thin andflexible envelope or shell made of vulcanized (cured) siliconeelastomer. The shell is filled either with a silicone gel or with anormal saline solution. The filling of the shell takes place before orafter the shell is inserted through an incision in the patient.

In the United States, women can choose between two different types ofbreast implant shell surfaces: a smooth surface and a textured surface.The surgeon generally recommends the type of surface based on his or hertechnique and the shape of the breast implant chosen to best fit theneeds of each patient.

Breast implants are not without complications, one of which is termedcapsular contracture. This is a complication that occurs uponcontraction of a fibrous outer capsule that forms around the implant,which tends to render the implant spherical and stiff and aestheticallyundesirable. According to the United States Food and DrugAdministration's (FDA) Breast Implant Consumer Handbook (2004), theliterature shows that textured surface breast implants may decrease thecapsular contracture rate.

Texturing may be provided in a number of ways. Silicone gel breastimplants covered with a thin layer of textured polyurethane foam enjoyedconsiderable popularity in the 1980s because of their remarkableresistance to the early development of fibrous capsular contracture. Forexample, U.S. Pat. No. 3,293,663 describes a soft gel-filled prosthesiswith a porous polyester fabric on the back side for tissue ingrowth andanchoring to the chest wall. Although these devices are no longeravailable in the U.S. because of regulatory constraint, their medicaland commercial success stimulated interest in surface texturization ofsilicone implants.

Despite many advances in the development of safe and comfortableprosthetic implants, there remains room for improvement.

SUMMARY OF THE INVENTION

The present invention provides a prosthesis suitable for implantation ina human being, for example, a breast implant suitable for use inreconstruction or augmentation of the human breast. The prosthesisgenerally comprises an implantable member, for example, an elastomericshell that is filled or is fillable with a liquid or gel. Theimplantable member has an exterior surface including one or morefixation regions defined thereon and configured, positioned orstructured to provide enhanced or controlled tissue ingrowth oradhesion.

In accordance with one aspect of the invention, the fixation surfacesare discrete, generally elongated surface portions extending across ananterior face or a posterior face of the implant. These fixationsurfaces, sometimes herein referred to as “fixation regions”, aregenerally defined by a texture, roughness or sheen that is differentfrom a texture, roughness or sheen of adjacent surface portions of theimplant.

In some embodiments, the fixation regions have an increased or enhancedtexture relative to the balance of the anterior face or posterior faceof the implant. In other words, the balance of the exterior surface maybe relatively less textured than the fixation regions. In someembodiments, the fixation regions are textured and adjacent surfaces,for example, the surface or surfaces that are not defined by thefixation regions, are substantially less textured, or are relativelysmooth.

The prosthesis may be structured to encourage enhanced tissue ingrowthor adhesion at the fixation regions, relative to an otherwise identicalsurface without such texture, roughness or sheen.

In one aspect of the invention, the fixation regions are positionedand/or configured such that the prosthesis, after implantation in thebody, moves more naturally with the human body, for example, in relativeunity with the muscles of the body. It is contemplated that because theimplant moves more naturally with the human body, the implant may beless prone to wear resulting from material stresses relative toconventional implants, for example, implants without such fixationregions. Furthermore, it is contemplated that the present implants willbe more comfortable to the patient in that they will move more naturallywith the body.

In a more specific aspect of the invention, the fixation regions may belocated at specific regions on an anterior face of the shell, that is, aface of the shell which faces the front of the human body when theimplant has been appropriately implanted in the human body.Alternatively or additionally, one or more discrete fixation surface maybe provided on a periphery of the shell (e.g. circumferentially) and/oron the posterior face of the shell, that is, the face of the shell thatfaces the back of the human body when the implant has been implanted inthe human body.

In an even more specific aspect of the invention, the fixation regionscomprise at least one elongated region located on the anterior face ofthe shell. The at least one elongated region may be, for example, aband-shaped region or alternatively, a plurality of band shaped regionshaving enhanced texture, roughness or sheen.

The elongated fixation regions may be positioned to align with one ofthe pectoralis major muscle groups or pectoralis minor muscle groups ofthe human body when the implant is implanted in the body. For example,in one embodiment of the invention, the at least one elongated regioncomprises a diagonally positioned band shaped region intended to alignwith the pectoralis major muscle group when the implant has beenimplanted in the body. In another embodiment, the at least one fixationregion comprises a plurality of elongated regions in a radiatingconfiguration generally copying the positioning of the pectoralis minormuscle group wherein the implant has been implanted in the body.

In another broad aspect of the invention, the prosthesis comprises abreast implant having a shell including a fixation region having a firsttexture and a balance of the shell surface having a second texture thatis different from the first texture. In other words, in some embodimentsof the invention, the entire, or substantially entire, exterior of thebreast implant shell is a textured surface with specific regions thereofhaving a greater degree of texturing relative to the remaining portionsof the textured surface.

It is contemplated that such different texturing will stimulate orencourage different degrees of tissue ingrowth or adhesion at thedifferent fixation regions. For example, in one embodiment, the firstfixation region is located on a posterior face of the implant and thesecond fixation region is located on an anterior face of the implant.The first fixation region may be defined by a texture that is moreconducive to tissue interaction and adhesion whereas the second fixationregion may be defined by a texture that is relatively less conducive totissue interaction and adhesion.

In yet another aspect of the invention, the prosthesis comprises a shellhaving an exterior structured to contact tissue, the shell including afirst fixation surface having a first open cell structure, and a secondfixation surface having a second open cell structure different than saidfirst open cell structure. In addition, the first fixation surface andthe second fixation surface are positioned to encourage respectivelydifferent degrees of tissue ingrowth or tissue adhesion by the body at abody-shell interface.

For example, the first open cell structure comprises relatively largeopen cells and the second open cell structure comprises relativelysmaller open cells. Alternatively or additionally, the first open cellstructure may comprise a first distribution of cells and the second opencell structure comprises a second distribution of cells wherein thefirst distribution of cells is relatively more dense than the seconddistribution of cells.

In yet another specific aspect of the invention, the first open cellstructure comprises relatively large rounded open cells and the secondopen cell structure comprises relatively small rounded open cells.Alternatively, the first open cell structure comprises relativelyrounded open cells and the second open cell structure comprisesrelatively angular open cells.

Advantageously, in accordance with certain embodiments, the first andsecond fixation surfaces are positioned and structured to be at leastsomewhat effective to disrupt or disorient capsular tissue formationabout the prosthesis after the prosthesis has been implanted in thebody.

The present invention further provides a breast prosthesis shell forimplantation in a human being, the shell manufactured by the steps ofproviding a shell precursor; applying a layer of silicone elastomer tothe shell precursor, applying solid particles of a first configurationto a portion of the layer of silicone elastomer and applying solidparticles of a second configuration to another portion of the layer ofsilicone elastomer before the layer is fully cured. After the layerincluding the solid particles embedded therein is cured, the solidparticles are then dissolved, for example, by means of a solvent thatdoes not dissolve the silicone elastomer to any appreciable extent. Theresulting elastomer shell includes a first open cell texture regionformed by said application of the solid particles of the firstconfiguration, and a second open cell texture region formed by saidapplication of the solid particles of the second configuration.

In yet another aspect of the invention, a method of augmenting orreconstructing a breast of a human being is provided. The methodgenerally comprises providing an implantable member including at leastone elongated fixation region as described elsewhere herein andimplanting the implantable member into a breast of a human being suchthat the fixation region generally aligns with one of the pectoralismajor muscle group and the pectoralis minor muscle group. The method mayfurther comprise filling the implantable member with a liquid or gelprior to or after the implanting step.

A further understanding of the nature and advantages of the presentinvention are set forth in the following description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become appreciatedas the same become better understood with reference to thespecification, claims, and appended drawings wherein:

FIGS. 1A-1B are a front view and a side elevational view, respectively,of an exemplary round breast implant of the present invention;

FIGS. 2A-2B are a front view and side elevational view, respectively, ofan exemplary shaped breast implant of the present invention;

FIGS. 3A and 3B are schematic views of a woman's upper torso showing,alignment of the pectoralis major muscle group and the pectoralis minormuscle group, respectively;

FIGS. 4A and 4B are vertical sectional views through a woman's breastand adjacent chest anatomy showing, respectively, subglandular andsubmuscular placement of a breast implant;

FIGS. 5A-5B are front and side elevational views of an exemplary roundbreast implant of the present invention having a generally elongated orband-shaped fixation surface;

FIGS. 6A-6B are front and side elevational views of an exemplary shapedbreast implant of the present invention having a generally elongated orband-shaped fixation surface;

FIG. 7 is a front elevational view of another breast implant inaccordance with the invention including a first fixation region having afirst texture and a second fixation region having a second texturedifferent from the first texture.

FIGS. 8A and 8B are front and rear elevational views of an exemplaryround breast implant of the present invention having a front texture anda rear texture that are different from one another.

DETAILED DESCRIPTION

The present invention provides a saline- or gel-filled soft implantshell, preferably a silicone elastomer shell, with a fixation surfaceover an exterior portion. The primary application for such soft implantsis to reconstruct or augment the female breast. Other potentialapplications are implants for the buttocks, testes, or calf, among otherareas.

The terms “fixation surface” or “fixation region”, as used herein,generally refer to a region or portion of an exterior surface of animplant which is positioned, structured or adapted to encourage tissueingrowth or adhesion at a body/implant interface. For example, afixation region may be a texture, roughness or sheen that is distinctfrom, for example, more pronounced than, adjacent surfaces of theimplant which do not encourage tissue ingrowth of adhesion to the samedegree as the fixation region. For example, other regions or surfaces ofthe implant exterior may be relatively smooth or less textured relativeto the fixation regions.

Such a fixation region may be formed by any suitable means, for example,but not limited to, a salt removal process such as described in U.S.Pat. No. 5,007,929, with appropriate changes being made. Alternatively,the fixation surfaces may be formed by separate textured elements suchas textured patches or films adhered to the outside of an otherwise“smooth” or less textured implant. Still, another method for forming thediscrete fixation regions may be by using a relatively roughened surfaceportion of a mold used to form the implant. Another method for formingthe present fixation regions includes texturing the exterior of theimplant after formation. The present invention should not be consideredlimited to any particular type of texturing or fixation surface, thoughthere might be certain advantages with one or more of these techniques.

Turning now to the Figures, FIGS. 1A and 1B are front and sideelevational views of an exemplary round breast implant 20 of the presentinvention. Generally, the implant 20 comprises an exterior surfacedefined by a relatively smooth anterior face 21, a textured posteriorface 22 and a textured peripheral region 24 located between the anteriorface 21 and the posterior face 22. The relatively smooth anterior facemay be a relatively less textured surface (relative to texture ofposterior face 22), such as, for example, a fine textured surface oreven a matte finish. In some embodiments, the implant 20 has arelatively smooth posterior face, a textured anterior face and atextured or smooth peripheral region. The fixation surfaces 22, 24themselves may have differing degrees of texturing. The diameter D andfront-to-back thickness T of the implant are shown and vary depending onthe patient's chest size and aesthetic considerations.

In the shown embodiment, the rear fixation surface 22 extends to theapex 26 or generatrix of the convex outer periphery of the implant 20.The peripheral fixation surface 24 continues forward a short distance Sonto the anterior or front surface 21. In some embodiments, the distanceS is between about 10% and about 30% of the thickness T. In someembodiments, the peripheral fixation surface 24 extends substantiallyentirely around the periphery of the implant 20, such that the implant20 is axi-symmetric. In other embodiments, the peripheral fixationsurface 24 may be abbreviated so as to extend around only a portion ofthe periphery of the implant, such as the inferior or superior half, orthe peripheral fixation surface may be broken up into spaced apartsegments. In some embodiments, the peripheral fixation surface 24comprises substantially evenly spaced segments resulting in alternatingsmooth and textured areas.

FIGS. 2A-2B illustrate an exemplary shaped breast implant 30 of thepresent invention having an inferior frontal lobe 32 simulating anatural breast. Like implant 20, implant 30 includes a rear fixationsurface 34 and a peripheral fixation surface 36. The width W, height H,and front-to-back thickness T of the implant are shown. If the frontprojection is round, then W=H, otherwise W may be greater than or lessthan H. When provided with a natural shape, the implant 30 has a properorientation, namely with the inferior lobe 32 at the lower center.Accordingly, the peripheral fixation surface 36 may extend completelyaround the periphery of the implant, or may be formed in discrete areasand be oriented relative to the natural shape of the implant. Forexample, the peripheral fixation surface 36 may be formed only aroundthe inferior or lower half of the implant, or may be formed only on thesides.

FIG. 3A illustrates a woman's upper torso schematically showing on oneside placement and alignment of the pectoralis major muscle group, whileFIG. 3B illustrates the placement and alignment of the pectoralis minormuscle group. These two muscle groups overlap one another and extendgenerally from the shoulder or collarbone region to the rib cageunderneath the breast. One aspect of the present invention is to providean implant including fixation surfaces such as described elsewhereherein, which are substantially aligned with these muscle groups whenthe implant is placed in the body.

While not wishing to be bound by any specific theory of operation, theregions or lines of contact of the implant with the primary chestmuscles experience greater movement than other areas of the implant notinterfacing the muscles. It is believed by the present inventors that byproviding a fixation region of the implant that is substantiallycoincident with or in substantial alignment with one or more of thesemuscle groups is more likely to remain secured (i.e., they move with themuscle). In addition, it is contemplated that such discrete fixationregions may provide the benefit of disrupting capsule formation and/orreducing the potential for capsular contraction.

FIG. 4A is a vertical sectional view through a woman's breast andadjacent chest anatomy showing a subglandular placement of a breastimplant 40. The implant 40 is positioned over the top of the pectoralismajor muscle group 42, which in turn overlays the pectoralis minormuscle group 44. The chest wall 48 showing a plurality of ribs 50 isalso indicated underneath the pectoralis minor muscle 44. FIG. 4B is avertical sectional view as in FIG. 4A but showing a submuscularplacement of the implant 40, underneath the pectoralis major musclegroup 42. Both these two implant placements are utilized primarilydepending on the surgeon's clinical determination, sometimes influencedby a dialogue between patient and the surgeon and desired outcome.Depending on the implant placements, the implant 40 may be in contactwith one or both muscle groups. In some embodiments of the invention,the implant includes substantially elongated fixation regions asdescribed and shown herein, and said fixation regions being insubstantial alignment with the appropriate muscle group which interfacethe implant when the implant is placed in the body.

For example, FIGS. 5A-5B are front and side elevational views of anexemplary round breast implant 60 of the present invention having aposterior face 62, a peripheral region 64, and an anterior faceincluding a elongated or band-shaped fixation region 66. The band-shapedfixation region 66 extends generally along a diagonal angle andcommences at the front border of the peripheral fixation surface 64. Theillustrated embodiment, the fixation region 66 has a substantiallyconstant width W as seen from the front in FIG. 5A. In one embodiment,the width W is between about 1 mm to about 20 mm, for example, betweenabout 2 mm to about 15 mm. Alternatively, although not shown, thefixation region 66 may have a configuration that is other than aconstant width.

In one embodiment, the band-shaped fixation surface 66 is generallyoriented or aligned with either the pectoralis major muscle group orpectoralis minor muscle group when the implant is implanted in thebreast. For instance, if the implant 60 is destined for a submuscularplacement such as in FIG. 4B, the fixation surface 66 may be oriented tobe generally aligned with the pectoralis major muscle group, as seen inFIG. 3A. Alternatively, the angle at which the insertion surface 66 isoriented may be an approximation of the average angle of the pectoralismajor and pectoralis minor muscle groups. In this way, the implant 60has a fixation surface 66 to encourage tissue ingrowth or adhesion alongthe major stress lines of the implant. Preferably, the fixation surface66 is angled between about 30-60° with respect to a vertical planethrough the implant 60. Of course, if the implant 60 is round as shown,the fixation surface 66 itself defines the orientation thereof. In oneembodiment, the band-shaped fixation surface 66 is centered about thecenter of the implant 60, therefore creating two symmetric orientationsabout 180° apart. This arrangement facilitates implant by providing twopossible orientations for the surgeon.

The band-shaped fixation region 66 may extend substantially across theanterior face of the implant and may be defined by a texture that isdifferent from a balance of the anterior face. The fixation region 66may also have a different texture, for example, a more pronounced ormore aggressive texture, than the rear fixation surface 62 or peripheralsurface 64.

FIGS. 6A-6B illustrate another exemplary shaped breast implant 70 of thepresent invention. The implant 70 again features a rear fixation surface72, a peripheral fixation surface 74, and a plurality of separateband-shaped fixation surfaces 76 a, 76 b, 76 c. These discrete fixationsurfaces 76 a, 76 b, 76 c are positioned or configured to align with oneor more of the muscle groups described above. For example, the threefixation surfaces 76 a, 76 b, 76 c may be generally oriented relative tothe fan-shaped pectoralis minor muscle group. Because the shaped implant70 is orientation-specific, proper placement of the implant orients thefixation surfaces 76 a, 76 b, 76 c with the particular muscle group. Asmentioned above, the various fixation surfaces 72, 74, 76 a, 76 b, and76 c may be formed with a similar level of roughness, or some may beless textured, such as with a matte finish. For instance, the rear andperipheral fixation surfaces 72, 74 may have a fine, matte finish, whilethe frontal fixation surfaces 76 a, 76 b, 76 c are more denselytextured. The present invention contemplates all permutations oftexturing choices.

In cross-section, the textured implant shells of the present inventionmay be single- or multi-layered. The overall thickness of the texturedimplant shell wall may be somewhat greater than a similar smooth-walledshell because of the extra layers of texture.

Turning now to FIG. 7, an anterior (front) view of another breastimplant of the present invention is shown generally at 110. The implant110 includes a shell 112 having an exterior surface including a firstfixation region 114 having a first texture 116 and a second fixationregion 118 having a second texture 122 that is different from the firsttexture 116. In the shown embodiment, the first texture 116 is a more“aggressive” texture than the second texture 122. The first texture 116is structured to encourage a greater degree of tissue interaction thanthe second texture 122.

In lieu of the second texture 122, it is contemplated that the secondfixation region 118, and perhaps the entire balance of the exterior ofthe shell 112, may be a low sheen surface, for example, a matte finish.

Turning now to FIGS. 8A and 8B, anterior (front) and posterior (rear)views, respectively, of another breast implant in accordance with theinvention are shown generally at 210. The implant 210 includes a shell212 having an anterior face 212 a and a posterior face 212 b, andincluding a first fixation region 214 having a first texture 216 and asecond fixation region 218 having a second texture 222 that is differentfrom the first texture 216. In the shown embodiment, the first texture216 may encompass the entire, or substantially entire, anterior face 212a of the implant 210. The first texture 216 is defined by a firstdistribution of pores, crevices or caverns that is relatively less densethan that of the second texture 222. The second texture 222, which mayencompass the entire, or substantially entire, posterior face 221 b ofthe implant 210, may be structured to encourage a greater degree oftissue interaction and adhesion than that of the first texture 216.

The shells 112 and 212 may be manufactured by a method of the inventioncomprising the steps of providing a shell precursor; applying a layer ofsilicone elastomer to the shell precursor, applying solid particles of afirst configuration to a portion of the layer of silicone elastomer andapplying solid particles of a second configuration to another portion ofthe layer of silicone elastomer before the layer is fully cured. Afterthe layer including the solid particles embedded therein is cured, thesolid particles are then dissolved, for example, by means of a solventthat does not dissolve the silicone elastomer to any appreciable extent.The resulting elastomer shell includes a first open cell texture regionformed by said application of the solid particles of the firstconfiguration, and a second open cell texture region formed by saidapplication of the solid particles of the second configuration.

One process for forming flexible implant shells for implantableprostheses involve dipping a suitably shaped mandrel into a siliconeelastomer dispersion. Many such dispersions are used in the field.Basically they contain a silicone elastomer and a solvent. The siliconeelastomer is typically polydimethylsiloxane, polydiphenyl-siloxane orsome combination of these two. Typical solvents include xylene or1,1,1-trichloroethane. Different manufacturers vary the type and amountof the ingredients in the dispersion, the viscosity of the dispersionand the solid content of the dispersion. Nonetheless, the presentinvention is expected to be adaptable to have utility with a widevariety of silicone rubber dispersions.

The mandrel is withdrawn from the dispersion and the excess siliconeelastomer dispersion is allowed to drain from the mandrel. After theexcess dispersion has drained from the mandrel at least a portion of thesolvent is allowed to volatilize or evaporate. Normally this isaccomplished by flowing air over the coated mandrel at a controlledtemperature and humidity. Different manufacturers use variousquantities, velocities or directions of air flow and set the temperatureand humidity of the air at different values. However, the desiredresult, driving off the solvent, remains the same.

It is also common for prostheses manufacturers to repeat this dip andvolatilize procedure a number of times so that a number of layers arebuilt up on the mandrel to reach a desired shell thickness. A layeredstructure like most current silicone elastomer shells can be made bysequentially dipping the mandrel in different dispersions.Alternatively, the steps may be repeated in a single dispersion so thatthe finished product is a single homogenous material or layer. That is,the dipping process may be done in multiple stages or steps, each stepadding more material, yet the finished product exhibits no distinctlayers and the entire shell wall is homogenous or uniform incomposition.

An exemplary process for forming the fixation surfaces on either amulti-layered shell or a single-layered shell will now be described.After the mandrel is raised out of the dispersion with what is to be thefinal layer adhering thereto, this layer is allowed to stabilize. Thatis, it is held until the final coating no longer flows freely. Thisoccurs as some of the solvent evaporates from the final coating, raisingits viscosity.

Again, it should be understood that alternative methods are contemplatedfor forming the flexible shell prior to the texturing process. The dipmolding process advantageously results in the flexible shell pre-mountedon a dipping mandrel, which can then be used for the texturing process.However, if the flexible shell is made by another technique, such as byrotational molding, it can subsequently be mounted on a dipping mandreland the process continued in the same manner.

Once the flexible shell has been stabilized and mounted on the mandrel,any loose fibers or particles are removed from the exterior of theshell, for example, with an anti-static air gun. A tack coat layer isthen applied. The tack coat layer may be sprayed on, but is desirablyapplied by dipping the flexible shell on the mandrel into a tack coatdispersion. The operator immerses the flexible shell into the dispersionand returns the mandrel to a rack for stabilization. The time requiredfor stabilization typically varies between 5-20 minutes. A suitable tackcoat layer is desirably made using the same material employed in thebase layers.

At this point, granulated solid particles (i.e., salt crystals) areapplied over that portion of the exterior surface that will end up asthe fixation surface. The solid particles may be applied manually bysprinkling them over the surface while the mandrel is manipulated, or amachine operating like a bead blaster or sand blaster could be used todeliver a steady stream of solid particles at an adequate velocity tothe coating on the mandrel. However, a preferred method of solidparticle application is to dip the mandrel/shell into a body of thesolid particles or expose it to a suspension of the solid particles. Itshould be understood that the present invention is not intended to berestricted to any one particular method of applying particles. Onepossible method to apply solid particles to some but not all of theshell is to mask off areas of the shell for which particles are not tobe applied and then apply the particles to the non-masked areas.

The tacky flexible shell may then be immersed in a fluidized(air-mixing) aqueous salt bath having regular cubic salt crystalsbetween about 10 to about 600 microns, or round crystals between about50-2000 microns or a combination thereof. Varying degrees of texturingmay be formed with the salt removal process by using differently sizedor shaped salt granules (for example, round salt crystals versus angularsalt crystals, large salt crystals versus relatively small saltcrystals, high density distribution of salt crystals versus relativelylow density distribution of salt crystals), on different areas of theshell. The shell is rotated for even coverage, removed, and then allowedto stabilize. After a suitable period of stabilization, such as betweenabout 5-20 minutes, the flexible shells may be dipped into an overcoatdispersion. A suitable overcoat dispersion may be made using the samematerial employed in the base layers. The flexible shells on themandrels are then mounted on a rack and allowed to volatilize, such as,for example, about 15 minutes.

The entire silicone elastomer shell structure is vulcanized or cured inan oven at elevated temperatures. The temperature of the oven ispreferably kept between about 200° F. and about 350° F. for a curingtime preferably between about 20 minutes and about 1 hour, 40 minutes.Upon removal from the oven, the mandrel/shell assembly is placed in asolvent for the solid particles, and the solid particles allowed todissolve. The solvent does not affect the structure or integrity of thesilicone elastomer. When the solid particles have dissolved, theassembly is removed from the solvent and the solvent evaporated. Theshell can then be stripped from the mandrel. At this point, it ispreferable to place the shell in a solvent for the solid particles andgently agitate it to ensure complete dissolution of all the solidparticles. When the shell is removed from the solvent, the solvent isevaporated.

Dissolving the solid particles leaves behind open, interconnected,cavities in the surface of the shell where the salt had been.

After finishing the shell according to the steps described above, thesteps required to make a finished breast implant prosthesis may besimilar to those known in the art. For example, an opening left by thedip molding process is patched with uncured sheeting, usually made ofsilicone rubber. Then, if the prosthesis is to be filled with siliconegel, this gel is added and cured, the filled prosthesis packaged, andthe packaged prosthesis sterilized. If the prosthesis is to be inflatedwith a saline solution, a one-way valve is assembled and installed, theprosthesis is post cured if required, and the prosthesis is thencleaned, packaged and sterilized. A combination breast implantprosthesis can also be made wherein a gel-filled sac is positionedinside the shell to be surrounded by saline solution.

In addition to the aforementioned dipping process, the flexible shellfor the prosthetic implant may be formed using a molding process. Forexample, a rotational molding process such as described in Schuessler,U.S. Pat. No. 6,602,452 the entire disclosure of which is incorporatedherein, may be used. The process for forming texturing on the exteriorsurface may be done using a dipping technique after the shell is molded,but another method is to roughen the inside of the mold. For example, amold having a generally smooth interior surface except for rough areasas described above will produce an implant shell having discretefixation surfaces. The rotational molding process is advantageousbecause the entire implant shell may be formed in relatively fewmanufacturing steps.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the scope of the invention, ashereinafter claimed.

What is claimed is:
 1. A prosthesis for implantation in a human being,the prosthesis comprising: an implantable member including an exteriorsurface defined by an anterior face and a posterior face; one of theanterior face and the posterior face including at least one generallyelongated fixation region defined by a texture, roughness or sheendifferent from a respective texture, roughness or sheen of a balance ofsaid one of the anterior face and posterior face; the prosthesis beingstructured such that when implanted adjacent a muscle group in a humanbeing, the fixation region can be generally aligned with an alignment ofsaid muscle group.
 2. The prosthesis of claim 1 wherein the implantablemember comprises an elastomeric shell.
 3. The prosthesis of claim 1wherein the fixation region has a first texture and said balance has asecond texture different from the first texture.
 4. The prosthesis ofclaim 1 configured for implantation in a breast of a human being andwherein the fixation region is positioned and configured to generallyalign with a pectoral muscle group when the prosthesis is so implantedin the breast of the human being.
 5. The prosthesis of claim 1configured for placement in a breast of a human being and wherein thefixation region is positioned to generally align with at least one of apectoralis major muscle group and a pectoralis minor muscle group whenthe prosthesis is so implanted in the breast of the human being.
 6. Theprosthesis of claim 1 wherein the at least one fixation region comprisesa plurality of fixation regions.
 7. The prosthesis of claim 1 whereinthe fixation region comprises a plurality of fixation regions in aradiating configuration.
 8. The prosthesis of claim 1 wherein thefixation region extends substantially entirely across the said one ofthe anterior face and the posterior face.
 9. The prosthesis of claim 1wherein the fixation region has as substantially constant width ofbetween about 2 mm and about 15 mm.
 10. A mammary prosthesis comprising:a implantable member including an exterior surface comprising at leastone generally elongated fixation region defined by a texture differentfrom a texture of the balance of the exterior surface; the at least onegenerally elongated fixation region being configured such that when theprosthesis is implanted in a breast of a human being, the generallyelongated fixation region generally aligns with an alignment of at leastone of a pectoralis major muscle group and a pectoralis minor musclegroup.
 11. The prosthesis of claim 10 wherein the exterior surface isdefined by an anterior face and a posterior face and the generallyelongated fixation region extends across at least one of the anteriorface and the posterior face.
 12. The prosthesis of claim 10 wherein theexterior surface is defined by an anterior face and a posterior face andthe generally elongated fixation region extends across the anteriorface.
 13. The prosthesis of claim 10 wherein the at least one generallyelongated fixation region includes a plurality of generally elongatedregions forming a substantially radiating configuration.
 14. Theprosthesis of claim 10 wherein the balance of the exterior surface issubstantially smooth.
 15. The prosthesis of claim 10 wherein theexterior surface is defined by an anterior face, a posterior face and aperipheral region between the anterior face and the posterior face, andthe fixation region extends along the peripheral region and across atleast one of the posterior face and the anterior face.
 16. A method ofaugmenting or reconstructing a breast of a human being, the methodcomprising: providing an implantable member including an exteriorsurface defined by an anterior face and a posterior face, wherein one ofthe anterior face and the posterior face includes at least one generallyelongated fixation region defined by a texture, roughness or sheendifferent from a respective texture, roughness or sheen of a balance ofsaid one of the anterior face and posterior face; and implanting theimplantable member into a breast of a human being such that the fixationregion of the implantable member generally aligns with one of thepectoralis major muscle group and the pectoralis minor muscle group. 17.The method of claim 16 wherein the at least one fixation region isdefined by an enhanced texture relative to said balance of said one ofthe anterior face and posterior face.
 18. A method of making a mammaryprosthesis comprising the steps of: providing a fillable elastomericshell having an exterior surface comprising an anterior face and aposterior face; and texturing only a portion of the exterior surface toform a band-shaped fixation region across at least one of the anteriorface and the posterior face.
 19. The method of claim 18 wherein the stepof texturing includes masking a balance of the exterior surface.
 20. Themethod of claim 18 wherein the band-shaped fixation region is shaped andpositioned to generally align with one of the pectoralis major musclegroup and the pectoralis minor muscle group.